Cameroon has seen a 'flood' of people as residents in Nigeria's far northeast
flee from their homes

Sustained Boko Haram attacks in Nigeria's far northeast have forced thousands of people from their homes, swamping towns in the north of neighbouring Cameroon, authorities said on Sunday.

"We've been flooded here in Mora by Cameroonians and Nigerians fleeing Boko Haram," a police officer in the northern town told AFP on condition of anonymity.

"The day before yesterday, there were already more than 10,000 people in Mora. Not a day goes by without more people coming."

The number of internally displaced people in Nigeria and those who have crossed its borders into Cameroon, Niger and Chad because of the militant violence has been increasing, with no end sight to the insurgency.

The United Nations' humanitarian office (OCHA) said on August 5 that Boko Haram attacks have forced nearly 650,000 people from their homes in the northeast states of Borno, Yobe and Adamawa.

Nigeria's National Emergency Management Agency has said nearly 11,500 fled Gwoza, also in Borno state, when militants seized the town on August 7. Boko Haram claims it has since declared Gwoza part of an Islamic caliphate.

The Cameroonian police officer said registration of the displaced had begun in Mora, while the nearby town of Kolofata had seen more than 6,000 arrive.

"People are everywhere: in schools, under trees and in the markets," he added.

"They're all coming from (Cameroonian and Nigerian) villages in the Kerawa area."

Kerawa straddles the border and has come under attack in recent days by Boko Haram, forcing the residents to flee on foot.

The Islamists, who have been fighting since 2009 to create a hardline Islamic state in northeast Nigeria, have taken control of the Nigerian part of the town and shelled the police station on the Cameroon side, the officer said.

Nigeria's military has denied that its soldiers also took flight and maintained they were instead pursuing the militants in a "tactical manoeuvre" when they found themselves on the other side of the border.

Cameroon state radio said the soldiers' withdrawal had led to a mass exodus of civilians, adding that more than 6,000 people had taken flight and were now based in the Kolofata state school, with 2,000 others around Mora.

Gamboru Ngala residents who fled across the border to the Cameroon town of Fotokol said on Saturday that the militants had begun to kill people "like chickens," despite initially targeting only the police and military.

The spokesman for the Roman Catholic diocese of Maiduguri also claimed militant fighters had carried out atrocities against Christians in the town of Madagali, in Adamawa state, but there was no independent corroboration.

Cameroon security sources said Gamboru Ngala was bombed from the air on Saturday night, but it was unclear whether it was a Nigerian or Cameroon air force operation.

Nigeria's This Day newspaper on Sunday quoted an unnamed source as saying that the country's military had retaken Gamboru Ngala.

But there was no immediate confirmation from defence headquarters in Abuja when contacted by AFP.